THat's a tough one.
I have an 09 Roubaix SL pro DA.
- Specialized Carbon crankset with OS BB (BB30)
- DA 7900 shifters
- DA 7900 chain
- DA 7900 Front Derailleur
I am less than impressed with (1) the spacing on the Specialized chainrings (Chainline) on their carbon BB30 crankset and (2) the pins/rivets for chain pickup on the large chainring.
With the position of the chainrings from the factory, they are not spaced correctly which makes proper front derailleur setup almost impossible. With no slack in the der. cable and in the small chainring position, and the Low limiter set in the right spot, When you shift into the large chainring, when the Derailleur clicks into the high gear, there is too much travel on the der (Or more likely the large chainring is too close to the small chainring) so the derailleur almost pushes the chain completely over and off the large chainring. So then you set the high limiter screw to keep from letting the derailleur over-shift but when you do, you never reach the SIS engagement click to lock it in the top position without way too much pressure on the lever.
So the fix for me was to leave some slack in the derailleur cable in the low gear position against the limiter. But this requires an excessive amount of stroke on the front (left) shifter which I can barely make with my smaller hands. But at least I don't have to worry about dropping the chain inside or outside or needing excessive force to get the FD locked in the large chainring position. Once in the proper gear, the cranks are great, but they don't shift well with the 7900.
It's really quite annoying.
Also, there are still 3 positions in the 7900 integrated shift lever for the FD even though they claim they have eliminated the trim settings. There is a trim setting for the small chainring, but not for the large. But with the large movement of the trim setting click and then the large chainring click, there's too much stroke for the specialized chainring spacing. It almost seems as though I have a tripple 7900 FD, but there is no such thing.
The pins on the inside of the large chainring are just flat rivets - no shape to them at all. Seems like they are about 8-9 years behind in technology there from shimano there - they even lag FSA in pin technology. my 2006 FSA chainrings have mre appropriately shaped pins.
Another word of advice - use a 7900 chain, but make CERTAIN you don't put it on inside-out. One side is now different than the other. My LBS put mine on inside-out and I had mad chain such in front from the Large to small chainring. After reading the manual, I realized the chain was on backwards, removed and installed it correctly, and now zero chain suck.
Good luck.
Any idea what that shimano adapter looks like? I am curious to see what it would take to change to a DA crankset.
The Specialized cranks are nice and stiff and seem to be well-made. Too bad the spacing seems way off.
Maybe the LBS messed something else up too though.
